In association with advances in electronic devices in recent years, nonaqueous electrolyte secondary batteries used as power supplies for the electronic devices are being strongly required to have high energy density and high output. Measures to cope with such a requirement include measures to increase the capacity of active materials, measures to increase the fill of an active material per volume, and measures to increase the charge voltage of batteries.
Known techniques for increasing the charge voltage of batteries include methods using a lithium transition metal oxide containing a halogen atom as a positive electrode active material (refer to, for example, Patent Literatures 1 to 4).